Correct type_resolver_util to set syntax=proto3 instead of syntax=proto2 on proto3 files.

PiperOrigin-RevId: 600473754

src/google/protobuf/util/type_resolver_util.cc

@@ -252,11 +252,14 @@ void ConvertFieldDescriptor(absl::string_view url_prefix,
 }
 
 Syntax ConvertSyntax(Edition edition) {
-  if (edition >= Edition::EDITION_2023) {
+  switch (edition) {
-    return Syntax::SYNTAX_EDITIONS;
+    case Edition::EDITION_PROTO2:
+      return Syntax::SYNTAX_PROTO2;
+    case Edition::EDITION_PROTO3:
+      return Syntax::SYNTAX_PROTO3;
+    default:
+      return Syntax::SYNTAX_EDITIONS;
   }
-  // TODO This should propagate proto3 as expected.
-  return Syntax::SYNTAX_PROTO2;
 }
 
 void ConvertEnumDescriptor(const EnumDescriptor& descriptor, Enum* enum_type) {

src/google/protobuf/util/type_resolver_util_test.cc

@@ -460,8 +460,7 @@ TEST_F(DescriptorPoolTypeResolverSyntaxTest, SyntaxProto3) {
   Type type;
   ASSERT_TRUE(
       resolver_->ResolveMessageType(GetTypeUrl("test.MyMessage"), &type).ok());
-  // TODO This should be proto3.
+  EXPECT_EQ(type.syntax(), Syntax::SYNTAX_PROTO3);
-  EXPECT_EQ(type.syntax(), Syntax::SYNTAX_PROTO2);
   EXPECT_EQ(type.edition(), "");
 }